qbit/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-11-11 23:20:24 -07:00
Code Releases Activity

spec: add section on the structure of interfaces

Browse Source 
This change introduces the notion of a structural interface
and its corresponding structural type.

Change-Id: Ib5442dfd04cb5950b4467428cae51849f8922272
Reviewed-on: https://go-review.googlesource.com/c/go/+/365474
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Robert Griesemer 2021-11-18 17:52:24 -08:00
parent a287c4aa38
commit e30ebaab0b
1 changed files with 62 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

66
doc/go_spec.html
View File

@ -1269,7 +1269,6 @@ func(int, int, float64) (float64, *[]int)
func(n int) func(p *T)
</pre>
<h3 id="Interface_types">Interface types</h3>
<p>
@ -1655,8 +1654,8 @@ ChannelType = ( "chan" | "chan" "&lt;-" | "&lt;-" "chan" ) ElementType .
<p>
The optional <code>&lt;-</code> operator specifies the channel <i>direction</i>,
<i>send</i> or <i>receive</i>. If no direction is given, the channel is
<i>bidirectional</i>.
<i>send</i> or <i>receive</i>. If a direction is given, the channel is <i>directional</i>,
otherwise it is <i>bidirectional</i>.
A channel may be constrained only to send or only to receive by
<a href="#Assignments">assignment</a> or
explicit <a href="#Conversions">conversion</a>.
@ -1836,7 +1835,6 @@ created by distinct <a href="#Type_definitions">type definitions</a>;
are different because <code>B0</code> is different from <code>[]string</code>.
</p>
<h3 id="Assignability">Assignability</h3>
<p>
@ -1928,6 +1926,66 @@ x T x is not representable by a value of T because
1e1000 float64 1e1000 overflows to IEEE +Inf after rounding
</pre>
<h3 id="Structural_interfaces">Structural interfaces</h3>
<p>
An interface <code>T</code> is called <i>structural</i> if one of the following
conditions is satisfied:
</p>
<ol>
<li>
There is a single type <code>U</code> which is the <a href="#Underlying_types">underlying type</a>
of all types in the <a href="#Interface_types">type set</a> of <code>T</code>; or
</li>
<li>
the type set of <code>T</code> contains only <a href="#Channel_types">channel types</a>
with identical element type <code>E</code>, and all directional channels have the same
direction.
</li>
</ol>
<p>
A structural interface has a <i>structural type</i> which is, depending on the
condition that is satisfied, either:
</p>
<ol>
<li>
the type <code>U</code>; or
</li>
<li>
the type <code>chan E</code> if <code>T</code> contains only bidirectional
channels, or the type <code>chan&lt;- E</code> or <code>&lt;-chan E</code>
depending on the direction of the directional channels present.
</li>
</ol>
<p>
Examples of structural interfaces with their structural types:
</p>
<pre>
type Celsius float32
type Kelvin float32
interface{ int } // int
interface{ Celsius|Kelvin } // float32
interface{ ~chan int } // chan int
interface{ ~chan int|~chan&lt;- int } // chan&lt;- int
interface{ ~[]*data; String() string } // []*data
</pre>
<p>
Examples of non-structural interfaces:
</p>
<pre>
interface{} // no single underlying type
interface{ Celsius|float64 } // no single underlying type
interface{ chan int | chan&lt;- string } // channels have different element types
interface{ &lt;-chan int | chan&lt;- int } // directional channels have different directions
</pre>
<h2 id="Blocks">Blocks</h2>